The long range goal of this project is to use morphological methods such as light and electron microscopy, freeze-fracture techniques, electron dense tracers, and immunochemical staining to study the lamellar structure of CNS myelin and mechanisms of myelin formation and breakdown. In vivo models of a CNS myelinated tract, the optic nerves of Xenopus tadpoles and the myelinated epiretinal fibers of the rabbit eye are used and current studies include myelinotoxic effect of cerebrospinal fluid from multiple sclerosis patients, methods to stain basic protein in myelin and oligodendrocytes and the appearance of myelin lesions produced by cycloheximide and hexachlorophene. BIBLIOGRAPHIC REFERENCES: Tabira, T., Webster, H. deF. and Wray, S.H.: In vivo test for myelinotoxicity of cerebrospinal fluid. Brain Res. 120: 103-112, 1977. Cullen, M.J. and Webster, H. deF.: The effects of low temperature on myelin formation in optic nerves of Xenopus tadpoles. Tissue & Cell 9: 1-10, 1977.